1. Field of the Invention
The present invention relates to a gasket, in particular, to a sheet gasket adapted to be inserted between flanges having different coefficients of thermal expansion.
2. Description of the Related Art
Compressed sheet gaskets comprising asbestos fibers joined by rubber binders are used in many industrial fields, and a swelling agent can be included in such a gasket to improve the sealing capability. Such a gasket is known as a "swelling sheet gasket". When such a swelling sheet gasket is used, however, and inserted between flanges having different coefficients of thermal expansion, for example, between a cylinder block of cast iron and a cylinder head of aluminum alloy, a problem arises in that the gasket is subjected to the repeated expansion and contraction of the flanges and is gradually forced out from the flanges, resulting in damage to the gasket.
To solve this problem, Japanese Utility Model Application No. 60-61524, filed by the same assignee as for the present case, proposed that an adhesive be coated on one side of the swelling sheet gasket to adhere the gasket to one of the adjoining surfaces of the flanges. The swelling sheet gasket is secured to that flange surface by adhesive force and expands and contracts together with the expansion and contraction of the flange surface, and the other side of the swelling sheet gasket slides relative to the other adjoining flange surface to protect the gasket from damage. Under experimental conditions, however, it became apparent that if the entire swelling sheet gasket including the adhesive coating surface area expands in water and oil, the adhesive force is reduced and stabilizing effect of adhering one side of the gasket to the adjoining flange is decreased.